This application relates to U.S. patent application Ser. No. 33,810, entitled "Ultrasonic Weld Location Mask and Method of Use" by Hawkins et al, filed Apr. 3, 1987; U.S. patent application Ser. No. 34,613, entitled "Variably-weighted Ultrasonic Welding Horn" by Welter filed Apr. 6, 1987; U.S. patent application Ser. No. 34,848, entitled "Ultrasonic Welding Wire Termination Apparatus" by Hawkins et al filed Apr. 6, 1987; and U.S. patent application Ser. No. 36,477, entitled "Apparatus for Ultrasonic Welding of Wires" by Welter et al filed Apr. 9, 1987; each of these applications being assigned to a common assignee with the present invention.
While the invention is subject to wide range of applications, it is especially suited for ultrasonically welding a conductor wire to an electrical terminal. In particular, the present invention is directed to the apparatus and method of using the apparatus whereby a conductor wire is ultrasonically welded to the channel portion of an electrical terminal.
The end of a metal conductor wire may be ultrasonically welded to a metal terminal having the wire firmly placed thereon. Typically, the terminal is placed on an anvil and an ultrasonic welding tip presses against the wire and the terminal to apply ultrasonic energy to the wire. The energy is applied so that the tip vibrates both the wire and the terminal to be welded so as to intermolecularly bond the metal workpieces to each other.
A typical example of this method of connecting a wire to an electrical terminal is disclosed in U.S. Pat. No. 3,717,842. The disclosure of this patent sets out a method whereby the conductor wire is first placed in the channel portion of an electrical terminal. Then, tabs forming part of the channel portion are crimped to close the channel portion so that the internal surface of the channel portion is in electrical contact with the wire. Then, the wire is ultrasonically welded to the channel portion. This patent can be distinguished from the present invention because the tabs are first crimped about the wire and then the ultrasonic energy is applied to the crimped tabs. By contrast, the present invention applies the ultrasonic energy directly to the wire which is resting on the electrical terminal. This important innovation produces a very low resistance weld.
Another aspect of the present invention is directed to confining the electrical terminal and moving the welding tip into the terminal to weld the wire thereto. In the past, the welding tip often came in contact with the walls of a support member. It has been found that the walls of the support member were subject to wear from the vibrations of the ultrasonic welding process. Therefore, the apparatus required rebuilding with new parts on a frequent basis. For example, in U.S. patent application Ser. No. 34,848, the tip of the ultrasonic horn contacts the walls of the supporting elements. Although the apparatus disclosed in the application Ser. No. 34,848 has been found to be very effective, it does require attention to wear of the support elements due to the vibration of the welding tip.
It is a problem underlying the present invention to provide an apparatus and method of ultrasonically welding an electric wire to an electrical terminal whereby the welding apparatus has an extended life expectancy and the weld between the wire and the electrical terminal has a very low resistance.
It is an advantage of the present invention to provide an apparatus and process for ultrasonically welding a conductor wire to an electrical terminal which obviates one or more limitations and disadvantages of the described prior arrangements.
It is a further advantage of the present invention to provide an apparatus and method for ultrasonically welding a conductor wire to an electrical terminal whereby the side walls of the electrical terminal are in contact with the welding tip of the ultrasonic welding device.
It is a yet further advantage of the present invention to provide an apparatus and process for ultrasonically welding a conductor wire to an electrical terminal whereby the electrical connection between the wire and the terminal has a very low resistance.
It is a still further advantage of the present invention to provide an apparatus and process for ultrasonically welding a conductor wire to an electrical terminal whereby the welding is very efficient and economical.
Accordingly, there has been provided an apparatus and process for ultrasonically welding a conductor wire to an electrical terminal. The terminal has a channel portion with a relatively unbroken internal surface for receiving one or more conductor wires and tabs forming part of the channel portion. The apparatus comprises an ultrasonic horn having a welding tip sized to enter the channel portion. Structure is provided for confining the electrical terminal and one or more conductor wires within the channel portion of the terminal adjacent the welding tip so that movement of the welding tip into the channel portion presses the conductor wire against the relatively unbroken surface of the electrical terminal to which it is to be welded.
The confining structure comprises a work support device having a U-shaped chamber for receiving the electrical terminal. The tabs of the channeled portion contact the walls of the U-shaped chamber to prevent contact of the welding tip with the chamber walls.